Lubricating oil composition

ABSTRACT

A GEAR OIL COMPOSITION COMPRISING A MAJOR AMOUNT OF A MINERAL LUBRICATING OIL CONTAINING LEAD NAPTHENATE AND SULFURIZED SPERM OIL AS EXTERME PRESSURE ADDITIVES, AND FROM 1 TO 2.5% BY WEIGHT OF FREE NAPTHENIC ACID, BASED ON THE WEIGHT OF THE COMPOSITION, SAID FREE ACID BEING EFFECTIVE TO IMPROVE THE WATER SEPARATION PROPETIES OF THE GEAR OIL WITHOUT DEGRADING OXIDATION STABILITY AND EXTREME PRESSURE CHARACTERISTICS.

United States Patent 3,558,511 LUBRICATING OIL coMPosmoN Calvin F. Rueping, Beaumont, Tex assignor to Texaco Inc., New York, N.Y., a corporation of Delaware No Drawing. Filed Nov. 17, 1967, Ser. No. 683,780 Int. Cl. C01m 1/24, N38

US. Cl. 252--37.2 5 Claims ABSTRACT OF THE DISCLOSURE A gear oil composition comprising a major amount of The use of lead naphthenate and sulfurized sperm oil as extreme pressure additives in gear oil compositions particularly those designed for the lubrication of machinery used in steel mills is well known. It has been found that the use of such gear oils was unsatisfactory because they exhibited poor water separation characteristics, i.e. these known gear oil compositions in use contained a relatively large amount of water in the form of an emulsion which was objectionable because the machinery gears were not being properly lubricated.

An object of the invention is to provide a new gear oil composition particularly useful in steel mills which obviates the poor water separation properties of the known gear oil compositions but retains the good oxidation stability and extreme pressure characteristics. Another object of this invention is to provide such a new and improved gear oil composition which functions ideally under the conditions of use.

These and other objects of the invention will become apparent from the following more complete description and appended claims.

Broadly, the gear oil compositions of the present invention comprises a major amount of a mineral lubricating oil component containing lead naphthenate and sulfurized sperm oil as extreme pressure additives, and free naphthenic acid in an amount between about 1 and 2.5% by weight, based on the weight of the composition, said amount of free naphthenic acid being effective to improve the water separation properties of the gear oil composition without degradation of oxidation stability and extreme pressure properties.

In a particularly desirable embodiment, this invention contemplates a lubricating oil composition particularly useful in steel mills which comprises lubricating oil, sulfurized sperm oil, lead naphthenate and an amount of free napthenic acid between about 1.5 and 2.5% by weight of the composition.

I have discovered, surprisingly, whereas lead naphthenate imparts poor water separation properties to gear oil composition for employment in. steel mills that by adding to the composition a critical amount of free napthenic acid the entire composition is unexpectedly improved in water separation characteristics. My discovery is considered particularly surprising in view of the fact that naphthenic acid is used to prepare the lead naphthenate component which is present in, the lubricating oil composition. It is considered particularly surprising to observe this phenomenon since naphthenic acid as lead naphthenate is present in the prior art composition. I have found, however, that it is necessary to employ at least 1.0% by weight of free naphthenic acid rather than in the salt form,

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as naphthenate, to obtain the desired good water separation characteristics. Amounts of free naphthenic acid below 1.0% by weight are relatively ineffective as far as any improvement in water separation characteristics of gear oil compositions containing same. I have also found that if the free naphthenic acid concentration in the gear oil composition exceeds about 2.5 by weight thereof the entire composition is rendered unsuitable for use as such excessive amounts of free naphthenic acid tend to promote oxidation and undue thickening of the gear oil which is also objectionable in steel mill machinery lubrication. The range of from 1.0 to about 2.5% by weight free naphthenic acid based on the total weight of the lubricating oil composition is considered critical. This percentage includes any free acidity contributed by the sulfurized sperm oil and the lead naphthenate components present in the composition i.e. the amount of free naphthenic acid is based on the total weight of the composition.

I have found that in preparing the lubricating oil composition of my invention that it is particularly desirable to employ the lead naphthenate additive when prepared by a method in which there is excess free naphthenic acid present therewith, but still within the prescribed range of 12. 5% by weight, basis the gear oil composition. This method enables the gear oil composition to be prepared without any independent step of adding the free naphthenic acid to the lubricating oil. However, it is to be understood that in preparing the gear oil composition of the present invention free naphthenic acid component can be added thereto separately.

The gear oil composition of my invention can 'be prepared in any suitable manner as by incorporating the lead naphthenate, free naphthenic acid and sulfurized sperm oil components to the base oil component and then mixing the components together until a homogeneous composition results. If desired, the base lubricating oil component can be mildly heated to facilitate incorporating the lead naphthenate, free naphthenic acid and sulfurized sperm oil into the oleaginous medium. Preferably, the composition contains 3 to 10% by weight of sulfurized sperm oil. The sulfurized sperm oil can be added to the base oil component together with the free naphthenic acid and the lead naphthenate components or independently. The sperm oil is preferably present in an amount between about 4 and 8% by Weight, particularly about 57% by weight. The lead naphthenate component is present in the composition in an amount that may vary between about 3 and 10% by weight, preferably about 5-7% by weight.

The lubricating oil forming the major component of the composition may be a mineral lubricating oil having a Saybolt Universal viscosity in the range of from about 150 to 4000 seconds at 100 F. and may be either naphthenic or paraffinic or mixed base in type or blends of such oils. The preferred lubricating oils are those having Saybolt Universal viscosities in the range of from about 175 to 3500 seconds at 100 F. A particularly preferred lubricating oil is a blend of 1'020% of a refined paraffin distillate oil having a Saybolt Universal viscosity of about 182 seconds at 100 F. and a -80% refined residual oil from a paraffinic crude having a SU viscosity of about 3500 seconds at F. (LOP Pale and BS. The lubricating oil component of the composition is present in amounts of from about 81 to 93% by weight particularly between about 85 and 91% by weight, based on the weight of the composition.

One may also incorporate a conventional anti-foam agent into the gear oil composition either during preparation of this composition or by incorporation into the finished composition. A suitable anti-foam agent is a silicone polymer oil having Saybolt Universal viscosity at 77 F. of 95-1-05 seconds with a typical analysis comprising 37.6% silicon, 32.3% carbon, 8.2% hydrogen and 21.9% oxygen by difference, weighing about 8.1 pounds per gallon. The silicone polymer oil is generally employed in very small quantities, i.e. on the order of 25-100 p.p.m. thereof, preferably 40-75 p.p.m.

In order to more fully illustrate the nature of the invention and the manner of practicing the same the following illustrative examples are set forth.

EXAMPLES I-II The respective lubricating compositions were all tested to determine if they met the specifications required by the evaluation factors of the Modified Wheeling Steel Demulsibility Test. The specifications for each phase of the test are set forth adjacent the results obtained when subjecting the gear oil compositions in the table below to the test factors.

Byway of explanation the Modified Wheeling Steel Demulsibility Test is designed to evaluate steel mill machinery gear oils containing extreme pressure additives. The test is performed on 360 milliliters of the gear oil which is mixed together in a special separatory funnel with 90 ml. of distilled water for minutes at 2500 rpm. at 180 F. on a constant temperature bath. Five hours after stirring was discontinued and using a ml. pipette, a 1-0 ml. sample of the mixed oil and water obtained from the center of the separatory funnel and 2 inches below the surface is withdrawn and the sample is discharged into a centrifuge tube. The amount of water present in the sample (after centrifuging for 10 minutes at a relative centrifugal force of 70-0) is determined by ASTM Method D 9 .6 and recorded as weight percent water in oil. After withdrawal of the 1 0 ml. sample the separatory funnel is removed from the constant temperature bath and any free water present therein is drawn off from the bottom and collected in a 100 ml. graduated cylinder. This withdrawn water is allowed to cool to room temperature and then the volume thereof is measured. The result is recorded as ml. of free water drained. After the free water, if any, has been withdrawn from the separatory funnel, the volume of liquid mixture therein is reduced to 100 ml. by carefully siphoning off the excess fluid from the top, the siphon tip being not more than about 20 mm. below the surface of the fluid at any time down during the siphoning period until the liquid level reaches the 100, ml. graduation mark on the wall of the separatory funnel. The 100 ml. of fluid then is drained into a centrifuge tube and centrifuged for at least 10 minutes at a relative centrifugal force of 700. The volume of separated Comparative Example A A base mineral lubricating oil blend of 15% by weight of a refined parafiin distillate oil having a Saybolt Universal viscosity of 182 seconds at 100 F. and 85% by weight of a refined residual oil having a Saybolt Universal viscosity of 3400 seconds at 100 F. was prepared by mixing the oils in the indicated amounts. There was added thereto with stirring p.p.m. of an anti-foam agent which contains 12.-1% by weight of silicon polymer, the silicone polymer having a viscosity of about 100 centistokes at 77 F. The resulting base oil blend had an API Gravity of 24.8 degrees, a flash point of 485 F. and a Saybolt Universal viscosity of 2000 at 100 F.

There was incorporated into 88% by weight of this base oil 6.0% by weight of sulfurized sperm oil having a saponification No. of 140, a total sulfur content of 11-12, a free sulfur content of 0.05 and an average Saybolt Universal viscosity of 240 seconds at 210 F. and 6% by weight of lead naphthenate containing 22.0% by weight of lead as PbO, and having a molecular weight of 315.

The gear oil composition was subjected to a Modified Wheeling" Steel Demulsibility Test and also to the Gear Lube Thickening Test which is described in detail hereinafter.

The Gear Lubricant Thickening Test involves passing 10 liters per hr. of dry air through a 300 ml. sample of the test oil which is maintained at 300 F. during the 100 hour test period. At the end of the test period the Saybolt Universal viscosity of the oil is determined at 210 F. From this value is subtracted the Saybolt Universal viscosity at 210 F. of the oil before the test and the remainder divided by 100 is reported as the percent viscosity increase at 210 F. A value of 20% or more is unacceptable since such an oil is unstable to oxidation. A satisfactory value is in the range 10-18% viscosity increase at 210 F.

The results are set forth in the table below.

EXAMPLES I-III Comparative Examples B and C Following the procedure of Comparative Example A, above, varying amounts of naphthenic acid were added to the composition to illustrate the effectiveness of this material in the prescribed amounts in improving the water separation properties of the composition without impairing the oxidation stability and extreme pressure characteristics of the composition.

BILITY AND OXIDA'ITON PROPERTIES Test Product A 1 2 3 B 0 limit Composition, wt. percent:

ase 0' 88. 0 87. 75 87. 50 87. 00 86. 00 85. O0 Suliurized sperm oil '6. 0 6. 00 6. 00 6. 00 6. 00 6. 00 Lead naphthenate 6. 0 6.00 6.00 6.00 6. 00 6.00 Naphthenic acid 0. 25 0. 50 1. 00 2. 00 3. 00 Test; results:

Free naphthenic acids by IR analysis 0. 82 1.07 1. 30 1. 80 2.80 3. 80 Modified wheeling steel, demulsibility test at 180 F.:

Percent, water in oil 0 0. 01 0 01 0.01 0. 01 0.01 l 1 Free water drained, rnl 24 5 56 71 69 68 Total free water, ml.-- 36 81 81 81 72 Z 55 Mayonnaise 0 0 0 0 0 0 1 2 Gear lube thickening test; 100

hours at 300 F.

Percent, viscosity increase at 1 Maximum.

2 Minimum.

3 1018% acceptable, 20% or over unsatisfactory.

Inspection of the table above shows that free naphthenic acids in the prescribed range of 1-2.5% provide excellent water separation properties to the gear oil compositions and little or no water in oil. Example A shows that less than 1% free naphthenic acid produces unsatisfactory test results, for example, the Total free water is well below the test minimum of 60 ml. Comparative Examples B and C show that exceeding the maximum limit of 2.5 free naphthenic acid while affording good demulsibility causes the composition to thicken excessively, above the typical working limit of 18%. Therefore these compositions are considered unsatisfactory. Exceeding the maximum limit of 2.5% by weight of free naphthenic acid in such a composition results in too great a percent viscosity increase, 20% or more, and indicates that the oil is oxidation unstable.

The terms and expressions used herein are terms of description and not of limitation, as there is no intention, in the use of such terms and expressions of excluding any equivalents, or portions thereof, except as might be set forth in the appended claims.

I claim:

1. A gear oil composition having improved water separation properties consisting essentially of a major amount of a mineral lubricating oil having a viscosity in the lubricating oil range and containing sulfurized sperm oil and lead naphthenate in amount sufiicient to lend extreme pressure properties to said gear oil, and from 1 to about 2.5% by weight of free naphthenic acid, based on the weight of the composition.

2. A lubricating oil composition according to claim 1 containing. an amount of free naphthenic acid between about 1.5 and 2.0 weight percent.

3. A lubricating oil composition according to claim 1 wherein the lead naphthenate is present in an amount between 4 and 8% and the sulfurized sperm oil is present in an amount between 4 and 8% by weight.

4. A lubricating oil composition according to claim 3 wherein the lead naphthenate is present in an amount of about 6% by weight and the sulfurized sperm oil is present in an amount of about 6% by weight.

5. A gear oil lubricating composition comprising 83 to 91% by weight of a blend of refined mineral lubricating oils, 4 to 8% by weight of sulfurized sperm oil, 4 to 8% by weight of lead naphthenate and 1 to 2.5 by weight of free naphthenic acid, said free naphthenic acid being effective to impart improved water separation properties to said composition without degrading oxidation stability and extreme pressure characteristics.

References Cited UNITED STATES PATENTS 2,730,506 1/1956 Sommer 2523\11.5

FOREIGN PATENTS 544,534 8/1957 Canada 25237.2

OTHER REFERENCES The Condensed Chemical Dictionary, 5th ed., 1956; p. 754.

DANIEL E. WYMAN, Primary Examiner I. M. HICKEY, Assistant Examiner US. Cl. XJR. 

